Ever since the invention of the reproducing piano around the turn of the twentieth century, there have been many attempts to develop a device which could accurately record and reproduce not only the registration of the notes played, but also the dynamics, those subtle gradations of piano volume which make piano performances especially pleasing to the ear. Despite seemingly primitive technologies, many of the types of instruments manufactured in the first half of the twentieth century provided the illusion of remarkable accuracy in their renderings, but the recording process very nearly always involved extensive editing, which sometimes took weeks for a single performance, before a reproducing piano roll record was ready for duplication and distribution. And, of course, the idea of a keyboard instrument recording device for home use was unthinkable, because of the great complexities and costs involved.
In the 1970's, the advent of the Pianocorder.TM. marked the first time such a home recording unit was offered to the public, but the quality of recording and reproduction was widely regarded as deficient. About the same time, Mr. Wayne L. Stahnke of Santa Monica, Calif. developed a quite accurate piano performance recording device which, however, was too complex and costly to be practical for home use. Mr. Stahnke's system, which was later embodied in very expensive Bosendorfer SE (Stahnke Equipped) pianos, was essentially based on the development work in the mid-to-late 1920's of Clarence N. Hickman, Ph. D. of the American Piano Company laboratories, which used a spark chronograph to sample positions of piano hammers in flight to provide data from which terminal hammer velocity was deduced. This information was later used in attempts to more accurately approximate the striking force of the hammers as originally produced by the pianists who recorded.
Mr. Stahnke's system was an important advancement in the state of the art. Nonetheless, in addition to its great cost, it did have significant technical and practical drawbacks. The system was very invasive to the piano, requiring extensive modification and surgery to the instrument. Optical sensors and shutters, instead of wire contacts, were used to sample hammer motion. This device had the disadvantage of sampling only two points in the hammer's travel, thus introducing the potential for error should the hammer strike twice before descending to the lower shutter position after a blow. Additionally, this arrangement requires careful adjustment so that the hammer sends a digital signal at the correct point in its travel lest the wrong amount energy be sent to the playback solenoid and/or at the wrong time. Therefore, the shutter adjustment must be fastidiously maintained by an expert technician.
A further drawback may be the inability to accurately record certain hitherto unmeasurable tonal characteristics which arise from variations of the pianists' differing approaches towards stroke. It has thus far not been conclusively proved that the terminal velocity of the hammer is the only variable in performance which affects tone. If it is not, the two-point sensor cannot be depended upon to furnish an accurate portrait of the tone produced by a pianist.
The traditional hammer sensors used in this scheme have always been too large to fit between the pinblock and action when removing the latter; also, their circuit boards, which are necessarily taller than the available one-eighth inch, have traditionally contained these sensors. Therefore, the pinblock has had to be cut down in size to accommodate this sensor assembly to permit convenient removal of the piano action for regular action and sensor maintenance.
Further, traditional ways of deducing the point in time at which the string is struck have depended upon assumptions made about time elapsed between the second activation of the optical sensor and the point of strike. These assumptions are highly dependent upon accurate regulation of the sensors and the flags passing through them, a condition extremely difficult to maintain, and are therefore not completely reliable.
As is well known to those skilled in the art, many attempts have been made to record hammer velocity by extrapolating from measurements of the velocity of the piano key. These have never been very satisfactory, since many unpredictable factors govern the relation of the hammer's motion to that of the key.
Another problem with previous schemes is that, as in the Stahnke instruments, graduated pedal motion was measured by means of precision potentiometers for reproduction. These had to be meticulously adjusted to give correct results, and were costly.
Motion of the individual dampers in some schemes has been extrapolated from the motion of the hammer as regards the time the damper lifts, and the moment of its descent has been flagged by a difficult-to-install optical or other switch beneath the keys requiring precise mechanical adjustment for accuracy. Thus, the damper information was merely an assumption.